Ionic liquid assisted electrospinning of quantum dots/elastomer composite nanofibers Jiahua Zhu a , Suying Wei b , Rahul Patil a , Dan Rutman a , Ashwini S. Kucknoor c , Andrew Wang d , Zhanhu Guo a, * a Integrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, TX 77710, USA b Department of Chemistry and Biochemistry, Lamar University, Beaumont, TX 77710, USA c Department of Biology, Lamar University, Beaumont, TX 77710, USA d Ocean NanoTech, LLC, 2143 Worth Ln., Springdale, AR 72764, USA article info Article history: Received 18 January 2011 Received in revised form 21 February 2011 Accepted 28 February 2011 Available online 8 March 2011 Keywords: Polymer nanocomposites Elastomer fibers Fluorescence abstract Quantum dots (QDs)/elastomer (VM) composite nanofibers have been fabricated via electrospinning method with the assistance of small amount (1 wt%) of ionic liquid. Without ionic liquid, polymer solution underwent an electrospraying process within the electric field and only individual droplets rather than continuous fibers were observed. Both fixed electrode and rotating disk electrode were used to collect the products. The latter one turned out to be much more advanced in collecting separated, aligned and narrow-size distributed composite nanofibers. With fixed electrode, even though nanofibers were obtained initially, the as-spun fibers were easily to merge together due to the flexible non-crys- talline nature of the VM chains and finally formed a condensed thin film. Strong fluorescent emission was observed in the composite nanofibers with a QD loading of 3 and 5 wt%, respectively. The optical property of QDs was not degraded after dispersing in the polymer solution as evidenced by the UVeVis absorption at 562 nm and 592 nm, and strong photoluminescent emission at 612 nm. In addition, differential scanning calorimetry (DSC) analysis revealed a strong interaction between ionic liquid and the polymer chains, which well explains the function of the ionic liquid on producing fiber structure of VM. An enhanced thermal stability of the elastomer in the composite nanofibers is observed as compared to that of the pure elastomer fibers. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Electrospinning technology has received growing interest recently owing to its comparatively low manufacturing cost and high yield for fabricating polymer fibers with diameters ranging from micrometers down to a few nanometers [1e4]. In a typical process, a polymer solution is forced through a syringe pump, forming a pendent drop at the tip of capillary. When the applied electric field strength (between the needle tip and the grounded collecting electrode) overcomes the surface tension force and viscoelastic force of the droplet, a polymer solution jet is initiated and accelerated toward the collecting electrode. As the jet travels through the air, the solvent evaporates and a non-woven polymeric fabric is formed on the target [5]. The resulting electrospun non- woven fibers possess a large specific surface area, high porosity and small pore size, which have equipped them vast potential applications such as gas separation [6], protein purification [7], scaffoldings for tissue engineering [8,9] and nano-electronics [10]. Viscoelastic elastomers, generally having high yield strain and low Young’s modulus, have been used in electrical actuators [11], adhesives [12] and soft tissue replacements [13] because of their high toughness and long-term durability. Ultrafine polymer fibrous structures become even more attractive for their potential appli- cations in filtration [7,14], wound dressing [15], drug delivery [16,17] and tissue scaffolds [18,19] after Reneker and co-workers developed new interest of electrospinning in 1990s due to their high specific surface area and the introduced unique physico- chemical properties. After that, large amount of different polymer fibers have been produced using the electrospinning method in the last two decades, including polyimide [1], polyacrylonitrile (PAN) [2], polyvinyl alcohol (PVA) [20], polystyrene (PS) [21] and etc. More detailed information regarding the polymer fiber species and electrospinning design would refer to the recent literature reviews [22,23]. However, it is really a challenge to electrospin elastomers into stable micron- and nano-fibers because of their low glass transition temperature and viscous surface, which make the * Corresponding author. Tel.: þ1 409 880 7654. E-mail address: zhanhu.guo@lamar.edu (Z. Guo). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2011.02.051 Polymer 52 (2011) 1954e1962